The older plots were complex and relatively slow-moving. Anchored abroad, they had multiple threads that could be unwound by U.S. or foreign intelligence. New efforts are likely to feature home-grown actors with few if any foreign ties - people who are U.S. citizens or here legally. These plots are best eliminated by quick action under those provisions of the USA Patriot Act that deal with business records, lone-wolf threats, calling records and roving wiretaps. Yet those are precisely the provisions that some in the Senate propose to hobble or eliminate in legislation sponsored by Judiciary Committee Chairman Patrick Leahy (D-Vt.).

The frequently reviled but rarely understood USA Patriot Act was passed in 2001. Later amended, it allows investigators to get court orders to examine business records in national security investigations by seeking such records from their custodians under Section 215; to focus on a national security target even when they cannot prove that he is affiliated with a particular terrorist organization or foreign power ("lone wolf" authority); to use "roving wiretaps" to track terrorists who switch cellphones frequently; and to get real-time access to the record of incoming and outgoing calls from a particular number (known as a pen register). The Obama administration initially supported leaving these authorities in place but has backtracked - a surprise considering that then-Sen. Barack Obama and then-Sen. Joe Biden voted to reauthorize this legislation in 2006. The threat has only grown, as Homeland Security Secretary Janet Napolitano recently noted.

Business records such as bank or telephone data examined early in an investigation can provide important leads. Details of how such data have been used remain classified, but the information is highly valued by investigators. Roving wiretaps, used for years in narcotics investigations, helped undo the 2009 plot to blow up a synagogue in the Riverdale section of New York. To understand the importance of "lone wolf" authority, consider that a computer seized from Zacarias Moussaoui, the "20th hijacker," during the summer of 2001 contained details of the Sept. 11 attacks, though Moussaoui was not known then to belong to a particular terrorist organization.

The current law permitting an intelligence agency to get information through a national security letter (NSL) requires a certification that the information relates to an agent of a foreign power, which would include a terrorist organization. The proposed legislation would remove the presumption of relevance from that showing and require also, before the information is examined, proof of how it relates to an investigation - which is to say, information may be sought only to confirm facts already known, not to investigate and determine what the facts are. The same illogical requirement would be imposed regarding phone records, even though one cannot know how numbers dialed to or from a telephone relate to an investigation until one knows what those numbers are and to whom they belong.

It bears emphasis here that such business and telephone records are information already in the hands of a third party, such as a bank or phone company, so the privacy interest of the subject is weak at best.

Sunset provisions terminating Section 215, roving wiretap, NSLs and "lone wolf" authority as of Dec. 31, 2013, are included, even though neither Osama bin Laden, Ayman al-Zawahiri nor Anwar al-Aulaqi is term-limited as of that date. The legislation imposes, for NSLs, additional after-the-fact administrative and judicial review, as well as evaluations by the Justice Department inspector general of the usefulness and importance of intelligence gathered (a judgment that office is not competent to make, institutionally or otherwise). Also, these functions to some extent duplicate oversight already conducted by the Privacy and Civil Liberties Oversight Board.

The net effect of imposing sunset provisions, changing presumptions and adding layers of review and other administrative and judicial burdens on use of these intelligence tools, absent evidence that any of them has been abused - and there has been none - is that intelligence professionals will regard these regimens as transitory. Confidence and initiative will be degraded. The wall between intelligence-gathering and criminal investigation, thought before Sept. 11 to have been required by statute or the Constitution, but realized afterward to have been unnecessary, will be rebuilt. If intelligence bureaucracies are taught that they incur only burdens and risk criticism by seeking to gather intelligence, they will revert to pre-Sept. 11 mode, and await the next cycle of criticism for failing to connect "dots" they have been discouraged from gathering. The existing procedures for obtaining even an "emergency" authorization under the Foreign Intelligence Surveillance Act already generate reams of documentation through several layers of bureaucracy; there is no need to find out how many more straws the camel's back can bear.

Michael V. Hayden was director of the CIA from 2006 to 2009. Michael B. Mukasey was U.S. attorney general from 2007 to 2009.